JP2001307733A - Sealed lead storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress shortening of cycle lifetime and rapid lowering of capacity in a sealed lead storage battery with a relatively large capacity and a wide area of negative plate. SOLUTION: This negative active material contains barium sulfate of not less than 1.5 wt.%, preferably 2.1 to 5.0 wt.% and lignin not less than 0.3 wt.% with respect to the mixed powder of lead and lead oxide. In addition the area of the negative plate is not less than 120 cm2, and the separator compression ratio given with A/B is not more than 1.2, where A is the thickness of the separator when pressured to 19,600 N/m2 A, and B is the thickness of the separator in the state of a plate group accommodated in the electric bath.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed lead-acid battery.

[0002]

2. Description of the Related Art Lead-acid batteries are widely used as main power sources for electric vehicles. Above all, sealed lead-acid batteries are widely used because they do not require rehydration work and have a high degree of freedom in installation direction. Since these batteries are used as a main power source, a deep discharge-charge cycle is mainly used.

In such a use mode, the capacity is 30
When a sealed lead-acid battery exceeding Ah is used, there is a problem that the cycle life is extremely reduced and the capacity is rapidly reduced after 100 cycles of charge and discharge. Such a sudden drop in capacity makes the equipment suddenly unusable, which is very inconvenient, especially for users of mobile equipment such as electric vehicles.

Such a decrease in capacity is a phenomenon that is hardly observed in a sealed lead-acid battery of about 15 Ah or less. Investigation of such battery deterioration factors revealed that the deterioration was due to a decrease in charge acceptability of the negative electrode plate.
Further detailed investigation revealed that the distribution of lead sulfate on the surface of the negative electrode plate was uneven, so that it was presumed that the charge / discharge reaction on the negative electrode plate was progressing unevenly.

[0005] The inventors of the present invention have made a study focusing on the fact that the above-mentioned deterioration of the negative electrode plate occurs particularly frequently in a battery having a large capacity. As a result, the degree of adhesion between the mat separator and the negative electrode plate is reduced. When the electrode plate area becomes larger than a certain degree, the degree of adhesion between the mat separator and the negative electrode plate greatly varies depending on the part of the negative electrode plate, and the deterioration of the negative electrode active material rapidly progresses at the part where the degree of adhesion is reduced. I understand.

[0006] The matte separator of a sealed lead-acid battery is impregnated with a dilute sulfuric acid electrolytic solution, so that sulfuric acid is replenished to the active material during discharging to maintain a discharging reaction, and sulfuric acid released from the active material during charging is charged. It has the effect of quickly absorbing from the active material to promote the charging reaction. Here, it was considered that due to the variation in the adhesion between the mat separator and the negative electrode plate, a portion where the adhesion was reduced was locally generated, and in particular, the progress was caused by inhibiting the charging reaction.

In order to construct a battery so that the adhesion between the mat separator and the negative electrode plate does not decrease, it is effective to increase the pressure (hereinafter referred to as group pressure) for compressing the electrode plate group in the electrode plate laminating direction. However, when the electrode plate area becomes larger than about 120 cm ² , the electrode plate area which is a force for pressing the electrode plate group ×
Since the group pressure rises and the stress applied to the battery case increases, there is a problem that the battery case itself is deformed in a commonly used battery case made of ABS resin or PP resin, so that a desired pressure cannot be obtained. . When the electrode group is inserted into the battery case, the electrode plate receives frictional resistance from the battery case wall. When the group pressure is increased, the frictional resistance increases in proportion to the increase in the group pressure. As a result, there is also a problem that the electrode plate itself is deformed.

Regarding the problem that the battery case is deformed and a desired pressure cannot be obtained, for example, as described in the specification of Japanese Patent No. 284388, the battery case is externally provided with a higher strength than a battery case material such as a metal plate. It is conceivable to bind around the battery case with a material having

However, there is no effective solution to the latter problem, that is, the problem that the electrode plate is deformed by frictional force when the electrode plate group is inserted into the battery case.
In particular, in the case of lead-acid batteries, the strength of the electrode plate itself is weak due to the use of a relatively weak current collector made of lead alloy, and the problem that this electrode plate is deformed is compared to other secondary battery systems. It is remarkable.

Therefore, it has been extremely difficult to improve the cycle life characteristics of a relatively large-capacity lead-acid battery by increasing the electrode group pressure.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to improve the cycle life characteristics of a relatively large-capacity lead-acid battery in which the electrode plate group pressure cannot be increased without impairing the productivity.

[0012]

According to a first aspect of the present invention, there is provided an electrode plate group comprising a positive electrode plate and a negative electrode plate laminated via a mat separator in a laminating direction. In a sealed lead-acid storage battery housed in a battery case in a pressurized state, the negative electrode plate is formed by kneading an active material paste obtained by kneading a mixed powder of lead and lead oxide (hereinafter referred to as lead powder) with a kneading solution, followed by aging and drying. In addition to the charged negative electrode active material, the negative electrode active material contains 1.5 mass% or more of barium sulfate based on the lead powder.

According to a second aspect of the present invention, in the sealed lead-acid battery having the structure of the first aspect, the amount of barium sulfate contained in the negative electrode active material is 2.1% by mass to 5% based on the lead powder. 0.0% by mass.

According to a third aspect of the present invention, in the sealed lead-acid battery having the structure of the first or second aspect, the negative electrode active material contains 0.3% by mass or more of lignin with respect to lead powder. It is decided to do.

According to a fourth aspect of the present invention, in the sealed lead-acid battery having any one of the first to third aspects, the area of the negative electrode plate is 120 cm ² or more.

Further, the invention according to claim 5 of the present invention is characterized in that the structure of the sealed lead-acid battery according to any one of claims 1 to 4 is such that the separator thickness at the time of pressurization of 19600 N / m ² is A, When the thickness of the separator contained in the battery case is B, the separator compression ratio given by A / B is 1.2 or less.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of a sealed lead-acid battery according to an embodiment of the present invention will be described.

For the negative electrode plate, polyester short fiber, carbon powder, sodium ligninsulfonate, and barium sulfate are added to lead powder, which is a mixed powder of lead and lead oxide produced by a ball mill method or the like, and mixed. Here, the amount of barium sulfate is preferably added at least 1.5% by mass or more, particularly in the range of 2.1% by mass to 5.0% by mass with respect to the lead powder. Also, sodium ligninsulfonate is added in an amount of 0.3% by mass or more based on the lead powder. After water was added to the lead powder containing these additives and water kneading was performed, sulfuric acid kneading was performed while adding dilute sulfuric acid to obtain an active material paste.

After filling this active material paste into a lattice of lead-calcium or a lead-calcium-tin alloy, it is aged and dried to form an unformed negative electrode plate. The area of the electrode plate except one ear of the negative electrode plate is 120 cm ² or more on one side.

As for the positive electrode plate, the positive electrode plate has the same configuration as the negative electrode plate, but the present invention does not particularly define the configuration of the positive electrode plate. Normally, an active material paste obtained by kneading lead powder similar to that of a negative electrode plate with water and dilute sulfuric acid is filled in a grid of a lead alloy substantially free of antimony such as a lead-calcium-tin alloy, aged and dried. A chemical positive electrode plate is formed. Here, lead red (Pb ₃ O ₄ ) can be added to the lead powder.

An electrode plate group is constituted by using the above-mentioned negative electrode plate and positive electrode plate. The negative electrode plate and the positive electrode plate are laminated via a mat separator such as glass fiber. Here, the thickness of the mat separator when pressed at 19600 N / m ² is Amm.

Next, the electrode plate group is housed in a battery case while being pressed in the electrode plate stacking direction. The separator is pressed in the thickness direction while the battery case is stored. The separator compression ratio given by the ratio A / B when the thickness of the separator in a pressurized state when the battery case is housed is B mm is 1.2 or less.

Thereafter, a sealed lead-acid battery is constructed according to a conventional method. As an example, a shelf portion is formed by collectively welding electrode plate lugs of the same polarity that constitute the electrode plate group. If necessary, after connection between adjacent cells is made, a lid is fitted to and joined to the battery case. Dilute sulfuric acid, which is an electrolytic solution, is injected from an injection port provided on the lid, and a battery case is formed. After completion of the battery case formation, a cap-shaped safety valve is attached to the liquid inlet, and an upper lid for holding the safety valve so as not to fall off the liquid inlet is joined to the lid, thereby completing the sealed lead-acid battery of the present invention.

It is widely known that barium sulfate or lignin is attached to a negative electrode plate in a conventional lead storage battery.
For example, for barium sulfate, 0.5%
It is common to add about 0% by mass of barium sulfate. The upper limit of the amount of barium sulfate is 2.0
It is on the order of mass%, and it has been considered unfavorable to add more than this amount, because this causes a decrease in the initial capacity and the like.

The inventors of the present invention have proposed a sealed type lead-acid battery in which the amount of electrolyte is limited by using a mat type separator, and in particular, the separator compression ratio is reduced to 1 because the negative electrode plate area per sheet exceeds 120 cm ^2. In a sealed lead-acid battery having a configuration as low as 0.2 or less, the amount of barium sulfate in the negative electrode active material is larger than the amount usually added, and at least 1.5% by mass or more, preferably 2.1% by mass with respect to the amount of lead powder. It has been found that the cycle life characteristic, which has been a problem in the conventional battery, can be improved by setting the content to 5.0% by mass or less. More preferably, the amount of sodium ligninsulfonate added to the negative electrode active material is 0.3
It has been found that more effect can be obtained when the content is not less than mass%.

[0026]

EXAMPLE Regarding Experiment 1, a preliminary experiment was conducted to determine what kind of battery in which the cycle life of a sealed lead-acid battery, which is the subject of the present invention, was significantly reduced.

As lead powder obtained by a ball milling method, 25% by mass of Pb + 75% by mass of PbO and 0.15% by mass of sodium ligninsulfonate with respect to the mass of the lead powder were added.
After adding and mixing 5% by mass of barium sulfate, a negative electrode active material paste was prepared by kneading with water and dilute sulfuric acid.

The negative electrode active material paste was filled in three types of negative electrode lattices, respectively, in lattice A, lattice B, and lattice C. Grating A has a height of 12.0 cm excluding ears and a width of 6.0 c.
m, and the electrode plate area per sheet (one side) is 72 cm ² . Lattice B has a height of 12.0 cm excluding ears and a width of 1
0.0cm, and the electrode plate area per sheet (one side) is 12
0 cm ² . Further, the grating C has a height of 1 excluding the ears.
3.0 cm ² , width 14.0 cm, and electrode plate area (one side) per sheet is 182 cm ² . Each of these lattice bodies has a thickness of 2.1 mm.

The negative electrode active material described above was applied to each of these lattice bodies.
Filled with material paste, aged and dried to form three types of negative electrode plates
Thus, a negative electrode plate A, a negative electrode plate B, and a negative electrode plate C were produced. Also,
Positive plates of the same dimensions to correspond to these negative plates
Is manufactured, and 19600 N / m ^TwoThickness A when pressurized is 2.2
mm combined with glass mat separator
A lead storage battery was manufactured. The separator compression ratio A
/ B (However, A = 19600 N / m^TwoPressurized separator
Thickness. B = Separation with electrode plates stored in battery case
The thickness of the sealed lead storage as shown in Table 1
A pond was made.

[0030]

[Table 1]

When the battery shown in Table 1 is trial manufactured, if the negative electrode plate area exceeds 120 cm ² , the separator compression ratio is set to 1.
When set to 4, that is, for the batteries B3 and C3, the frequency at which the deformation of the electrode plates occurs when the electrode group is stored in the battery case is 40.
%, Which was found to be inconvenient in actual production.

Next, the batteries shown in Table 1 were subjected to a cycle life test under the following conditions. However, for the batteries B3 and C3 in which a large number of electrode plates were deformed at the time of the trial production, those having no electrode plate deformation were selected and subjected to a cycle life test under the following conditions.

Cycle Life Test Conditions Charge 14.7V Maximum current 0.6CA 8 hours Discharge 0.25CA 10.5V Discharge end Test ambient temperature is 25 ° C.

The charge / discharge cycle was repeated under the above conditions, and the number of cycles at which the discharge duration became 50% or less of the initial value was defined as the life cycle. FIG. 1 shows the test results.

From the results shown in FIG. 1, the area of the negative electrode plate was 70 c.
m ² and a battery that is, battery A1, a battery A2, a battery A3
Although the life gradually decreases as the separator compression ratio decreases, no sharp reduction in life is observed, and the rate of capacity reduction during the life test is slow. However, as the area of the negative electrode plate increases to 120 cm ² , the number of life cycles sharply decreases. Further, when the separator compression ratio is set to 1.2 or less, it can be confirmed that the capacity rapidly decreases after 100 cycles.

Regarding Experiment 2, a cycle life test was performed on the 12V28Ah battery in which the cycle life was reduced in Experiment 1 under the same conditions as in Experiment 1 by changing the addition amount of barium sulfate and the addition amount of ligninsulfonic acid in the negative electrode active material. Was. Here, the configuration of the 12V28Ah battery is the same as the configuration of the battery used in Experiment 1. That is, the number of positive electrode plates constituting one cell is three, the number of negative electrode plates is four, and the area per one negative electrode plate is 120 cm ² on one side.

Table 2 shows the structure of the battery manufactured in Experiment 2.

[0038]

[Table 2]

A cycle life test was performed on the batteries shown in Table 2 under the same conditions as in Experiment 1. The results are shown in FIG. 2 for the battery B1 series and in FIG. 3 for the battery B2 series.

From the results shown in FIGS. 2 and 3, when the amount of barium sulfate is increased to 1.5% by mass, the number of life cycles starts to increase.
It can be seen that a stable cycle life can be obtained. Further, particularly when the amount of barium sulfate added is 2.1% by mass or more, the amount of sodium ligninsulfonate is reduced to 0.1%.
By setting the content to 30% by mass, it is possible to make the transition of the battery capacity in the cycle life test a gradual decrease instead of a sudden decrease. Such a gradual decrease in the capacity allows the user of the device to recognize the deterioration of the battery as described above, which is convenient for estimating the battery life on the device side.

When the batteries of the present invention were disassembled and inspected after the end of the life test, lead sulfate was uniformly distributed on the negative electrode plate, and the charge / discharge reaction proceeded relatively uniformly. It was speculated that it could be suppressed.

The upper limit of the amount of barium sulfate is preferably 5.0% by mass or less based on the lead powder. Even if the addition amount of barium sulfate is 7.0% by mass or more, it is not appropriate because a longer life extension effect cannot be obtained and the capacity tends to decrease remarkably.

[0043]

As described above, according to the present invention,
In a sealed lead-acid battery having a relatively large capacity, it is possible to suppress a decrease in cycle life and to suppress a sudden decrease in capacity that has conventionally occurred. Further, since it is not necessary to increase the electrode group pressure to such an extent that productivity is reduced, and a life extension effect can be obtained with a relatively low electrode group pressure, it is extremely useful in industry.

[Brief description of the drawings]

FIG. 1 is a diagram showing the cycle life characteristics of a battery in Experiment 1.

FIG. 2 is a diagram showing the cycle life characteristics of the battery for the battery B1 series in Experiment 2.

FIG. 3 is a diagram showing the cycle life characteristics of the battery for the B2 series in Experiment 2.

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Claims (5)

[Claims] 1. A sealed lead-acid battery in which an electrode group in which a positive electrode plate and a negative electrode plate are stacked via a mat separator is housed in a battery case while being pressed in the stacking direction, the negative electrode plate is composed of lead and lead acid. Active material paste obtained by kneading a mixed powder of the compound with a kneading liquid is provided with a negative electrode active material obtained by aging, drying, and then forming and charging, and the mixed powder of lead and lead oxide is contained in the negative electrode active material. A sealed lead-acid battery containing at least 5% by mass of barium sulfate. 2. The negative electrode active material according to claim 1, wherein barium sulfate is contained in an amount of 2.1% by mass to 5.0% by mass based on the mixed powder of lead and lead oxide. Sealed lead-acid battery. 3. The hermetic seal according to claim 1, wherein the anode active material contains 0.3% by mass or more of sodium ligninsulfonate based on a mixed powder of lead and lead oxide. Lead-acid battery. 4. The sealed lead-acid battery according to claim 1, wherein the area of the negative electrode plate is 120 cm ² or more. 5. The separator compression given by A / B, where A is the thickness of the separator when pressurizing at 19600 N / m ^2, and B is the thickness of the separator when the electrode group is housed in the battery case. 5. The sealed lead-acid battery according to claim 1, wherein the ratio is 1.2 or less.